Most rv plumbing is 1/2 inch PEX with some type of crimp on connectors. The most common way to repair them, I did one a few weeks ago on my rig is to remove the crimps and replace the T joint and re-crimp the connectors.
Parts and tools to do this can be purchased at most any big box or hardware store.
Hope you can get is repaired, it does not sound like a big job but leaving it can cause more problems.
Here is a link to some one who did it on here:
Many find the hardest part is accessing the work
Good luck, I am sure others will give you some more options.
2011- 351RLTS Eagle, MorRyde suspension/pin box,
2017- F350 6.7 PSD Lariat FX4,SRW, SB,CC
Hughes PWD SP-50A, TST TPMS
Gator roll-up bed cover
B&W Turnover ball, Andersen Ultimate 3220
Can't find what you're looking on JOF? Try Jayco Owners Forum Custom Google Search